WO1999011465A1

WO1999011465A1 - Printer for effecting bidirectional printing and method of adjusting the printing position therefor

Info

Publication number: WO1999011465A1
Application number: PCT/JP1998/003908
Authority: WO
Inventors: Hironori Endo
Original assignee: Seiko Epson Corporation
Priority date: 1997-09-02
Filing date: 1998-08-31
Publication date: 1999-03-11
Also published as: DE69834802D1; DE69834802T2; EP0938977A4; EP0938977B1; US6158905A; EP0938977A1

Abstract

The value for adjusting the printing misregistration between one way and the return way is determined for each of the printing papers having different widths. The printing misregistration is adjusted by, for example, changing the frequency of drive clock signal given to the print head in the direction of horizontal scanning. The frequency of drive clock signal is separately set for each of regions defined by dividing the horizontal scanning range.

Description

Specification

TECHNICAL FIELD The present invention relates to a printer for performing bidirectional printing and a printing position adjusting method therefor.

The present invention relates to a technique for printing an image on a print medium while performing main scanning in both directions in a reciprocating manner, and more particularly, to a technique for adjusting a deviation (printing deviation) of a printing position in a main scanning direction in a forward path and a return path. is there. Background art

2. Description of the Related Art In recent years, as a computer output device, a type color printer that discharges several colors of ink from a head has been widely used. Some of such color printers have a function of performing so-called "bidirectional printing" in order to improve printing speed.

In bidirectional printing, the printing position in the main scanning direction on the forward path and the return path is reduced due to the backlash of the drive mechanism in the main scanning direction, the extension of the carriage belt, and the warpage of the platen supporting the print medium below. The problem of misalignment is likely to occur. As a technique for resolving such printing misalignment, for example, a technique disclosed in Japanese Patent Application Laid-Open No. Hei 5-69625 disclosed by the present applicant is known. In this prior art, the shift amount (print shift amount) of the print position in the main scanning direction is registered in advance, and the print position in the forward path and the return path is corrected based on the print shift amount.

By the way, various types of print media such as A3 paper, A4 paper, and postcards are used. Normally, A3 and A4 papers are inserted and printed almost at the center of the main scanning range of the printer, but postcards are inserted and printed near the edge of the printer. The printing shift tends to be particularly large at both ends of the main scanning range of the printer. For this reason, even if the print misregistration was properly adjusted for A3 paper or A4 paper, there was a problem that the print misregistration for the postcard could not be properly adjusted. The present invention has been made to solve the above-mentioned problems in the prior art. (1) It is an object of the present invention to provide a new technology for a printer that performs bidirectional printing, in order to reduce a deviation of a printing position in a main scanning direction between a forward pass and a return pass. Disclosure of the invention

In order to solve at least part of the above or other problems, there is provided a printer having a bidirectional printing function for printing an image on a print medium while performing main scanning in both directions in a reciprocating manner. The printer moves the print head, the print head and the print medium at least relatively in the main scanning direction and the sub-scan direction, and drives the print head to print on the print medium. And a control unit for controlling the driving mechanism. The control unit is configured to control the print head in the main scan direction so that the print position in the main scan direction in the forward pass substantially matches the print position in the main scan direction in the return pass according to the position of the print head in the main scan direction. A print misalignment adjustment unit that adjusts a print position in at least one of them is provided.

The print misalignment adjustment unit may adjust the print position according to an actual main scanning range of the print head and a position of the print head in the main scan direction. The control unit further includes an adjustment value memory that stores an adjustment value used for adjusting the print position for each of a plurality of print media having different widths in the main scanning direction. The adjustment value may be read from the adjustment value memory according to the width of the print medium in the main scanning direction that is actually used, and the printing position may be adjusted according to the read adjustment value. .

The printer may further include a memory that stores data for printing a plurality of print misalignment inspection patterns corresponding to the plurality of print media. The adjustment value of the printing deviation may be corrected using an offset corresponding to the thickness of the printing medium used.

The print misalignment adjustment unit may adjust the print position at a central position in the main scanning direction of each of the plurality of recording media. Further, the print misalignment adjustment unit may adjust the print position at a plurality of positions in the main scanning direction of each of the plurality of recording media.

In such a printer, it is possible to perform appropriate adjustment of print misregistration for a plurality of recording media.

In an embodiment, the print shift adjusting unit generates a drive clock signal to be given to the print head, and changes a frequency of the drive clock signal in at least one of the forward path and the return path along the main scanning direction. And a driving clock generating unit for driving.

The drive clock generation unit may individually set the frequency of the drive clock signal in a plurality of areas that divide the main scanning range.

The driving clock generation unit generates an adjustment value memory that stores a parameter for setting a frequency of the driving clock signal for each of the plurality of regions, and generates a reference clock signal having a predetermined reference frequency. A reference clock generation unit, a frequency conversion unit that generates the drive clock signal by converting the frequency of the reference clock signal using a parameter read from the adjustment value memory; and A parameter setting unit that determines which of the plurality of regions the main scanning position of the pad is included in, reads a parameter corresponding to the region including the main scanning position from the memory, and sets the parameter in the frequency conversion unit. And may be provided.

The parameter setting unit may change a division of the plurality of areas and a value of the parameter according to a width and a thickness of a print medium in a main scanning direction to be used.

In such a printer, the shift of the printing position in the main scanning direction between the forward path and the return path can be reduced by changing the frequency of the drive clock signal in at least one of the forward path and the return path along the main scanning direction. .

The present invention further provides printing using a printing head while performing bidirectional main scanning in both directions. It is also directed to a method of adjusting a printing position in a main scanning direction in a printer that prints an image on a medium. In this method, at least one of the forward path and the return path is adjusted so that the print position in the main scan direction on the forward path and the print position in the main scan direction on the return path substantially match in accordance with the position of the print head in the main scan direction. The printing position is adjusted in. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual diagram of an ink jet printer to which the present invention is applied.

FIG. 2 is a diagram showing an example of adjustment of print misalignment,

FIG. 3 is a diagram showing an example of a print misalignment inspection pattern.

Fig. 4 is a graph showing the result of adjusting the print shift in the main scanning direction of the ink jet printer.

FIG. 5 is a diagram showing another example of a print misalignment inspection pattern.

FIGS. 6 (a) and 6 (b) are diagrams showing still another example of the print misregistration inspection pattern.

FIG. 7 is an explanatory diagram showing a schematic configuration of a printer 22 as one embodiment of the present invention, FIG. 8 is an explanatory diagram showing a schematic configuration of a dot recording head of the printer of the present invention, and FIG. Explanatory diagram showing the principle of dot formation in the printer of the present invention,

FIGS. 10 (a:) to 10 (e) are explanatory diagrams showing a method for correcting a printing shift in bidirectional printing in the embodiment.

FIG. 11 is a block diagram showing the internal configuration of the drive clock generation circuit 44, and FIG. 12 is a block diagram showing another configuration of the drive clock generation circuit 44. BEST MODE FOR CARRYING OUT THE INVENTION

A. Correction of print misalignment according to printing paper

FIG. 1 is a conceptual diagram of an ink jet printer to which the present invention is applied. The ink jet printer includes a control unit 200 and a drive mechanism unit 300. Control unit 2 Reference numeral 00 denotes a print shift adjustment value memory 202, a print shift adjustment unit 204, and a print shift inspection pattern memory 206. Further, the drive mechanism section 300 includes a print head 302, a carriage motor 304, a paper feed motor 306, and a paper sensor 308.

The print shift inspection pattern memory 206 stores parameters for printing a print shift inspection pattern as described later. The types of printing paper that can normally be used in printers are somewhat limited. The print shift adjustment value memory 202 stores print shift adjustment values (5 1, (5 2, 6 3...) For each print sheet determined using the test pattern for each print sheet. Is stored.

The type of printing paper actually used for printing (that is, the width of the printing paper) is detected by the paper sensor 308. The paper sensor 308 detects the type of printing paper actually used for printing from a plurality of types of printing paper registered in advance. The print misalignment adjustment unit 204 sets the adjustment value 5 suitable for the printing paper actually used for printing.

The drive mechanism unit 300 is controlled using 1 (the subscript i indicates the i-th printing paper) to adjust the printing misalignment.

As a specific method of adjusting the printing deviation, a method of adjusting the frequency of the drive clock signal supplied to the print head 302 as described later can be adopted, or any other method can be used. It is also possible to employ.

FIGS. 2 (a) and 2 (b) are diagrams showing adjustment of print misalignment using a print misalignment inspection pattern. As shown in FIG. 2A, the inspection pattern 402 is formed by printing a plurality of dots arranged in the sub-scanning direction on the outward path and printing a plurality of dots arranged in the sub-scanning direction on the return path. You. The amount of deviation in the main scanning direction between the dot row printed on the forward path and the dot row printed on the return path △ X force <<, is detected as a print deviation in bidirectional printing. The detection of the print misregistration amount Δχ can be performed visually, or can be automatically performed using an optical position detection device (not shown). Fig. 2 (b) is printed so that the print shift amount △ X shown in Fig. 2 (a) becomes 0. This shows a state in which misregistration has been adjusted. The adjustment amount of the print misalignment <5 (here, (5 = △ x)) can be input by the adjuster, or the adjustment amount can be automatically determined from the detection result of the optical position detection device, for example. It is.

FIG. 3 is a diagram illustrating an example of a print misalignment inspection pattern for a plurality of types of printing paper. Here, the print misalignment inspection pattern is located at the center position in the main scanning direction of each of the three types of printing paper 40 "1a, 401b, and 401c, which are A3 paper and A4 paper. The print misalignment is adjusted by adjusting the center position in the main scanning direction with respect to each of the plurality of printing papers so that the misalignment of the print misalignment inspection pattern 402 becomes zero. Respectively.

For example, the determination of the print shift adjustment amount 5i for an inkjet printer in which the maximum size of print paper that can be used is A3 is performed as follows. First, in order to print the print misalignment inspection pattern at the center position in the main scanning direction of a plurality of usable printing papers (A3 paper, A4 paper, postcard), an inspection pattern for each printing paper is used. The data to be represented are created and stored in the print shift inspection pattern memory 206. This inspection pattern data is commonly used by printers of the same model. Then, as shown in FIG. 3, a printing misalignment inspection pattern suitable for the printing paper is printed on each printing paper, and the printing misalignment ΔX in these inspection patterns 402 is measured. Then, the print shift adjustment values in bidirectional printing <5 1, 6 2, (5 3...) Are determined so that the print shift amount ΔX becomes zero. The print shift adjustment values S 1, δ 2, (5 3 ... are stored in the print shift adjustment value memory 202. The print shift amount Δ 異なる is different for each printer, even for printers of the same model. A different value is also set for each printer for 51, δ 2, <5 3 .. Therefore, the print shift adjustment value memory 202 stores the adjustment value 51, δ 2, <5 for each printer. It is preferable to use a rewritable nonvolatile memory so that 3 can be written.

Fig. 4 is a graph showing the distribution of the print shift amount AX on a plurality of printing papers with different paper widths. It is rough. Here, it is assumed that each print sheet is fed in accordance with the left end of a printer input tray (not shown). The print shift adjustment value for each print sheet is adjusted so that the print shift amount △ X at the center position of the width in the main scanning direction for each sheet 4 0 4 a, 4 0 4 b, 4 0 4 c is zero. Has been determined respectively. That is, in the example of FIG. 4, the adjustment value for each printing paper is set appropriately, and as a result, the printing quality is prevented from deteriorating for each printing paper due to print misalignment. Since the print misalignment increases at both ends of the printable area (scannable area of the print head) along the main scanning direction of the printer, temporarily print to fit A3 paper, which has the maximum paper width that can be fed If the misalignment is adjusted, it may not be possible to properly adjust the misalignment of the postcard with a small paper width. On the other hand, as shown in Fig. 4, if a different adjustment value is used for each printing paper, it is possible to appropriately adjust the printing deviation even for printing paper with a small paper width such as a postcard. This has the effect. Note that the adjustment value for each print sheet is stored in the adjustment value memory 202, so that it is not necessary to adjust the print sheet once adjusted.

Note that the width in the main scanning direction differs depending on the paper feeding direction even for the same size printing paper (that is, the width in the main scanning direction differs vertically and horizontally). Also, the width in the main scanning direction may be the same for different sizes of printing paper depending on the paper feeding direction. For example, the width in the main scanning direction is the same for A3 paper portrait orientation and A4 paper landscape orientation. In consideration of such various cases, it is preferable that the adjustment of the printing misalignment is performed not according to the size of the printing paper but according to the width along the main scanning direction when the printing paper is fed.

FIG. 5 is a diagram showing another example of the print misalignment inspection pattern. In this example, instead of printing the inspection pattern on a plurality of printing papers with different paper widths, the print misregistration inspection pattern for all the printing papers is placed on the widest A3 paper 401a. Is printed.

In a specific procedure, for example, the maximum size of printable paper is A3 paper. When printing, the data for printing the print misalignment inspection pattern for A3 paper, A4 paper, and postcard on one sheet of print paper is created, and the print misalignment inspection pattern memory 206 is prepared in advance. Is stored in advance. Then, the print misalignment inspection pattern is printed on a single print paper (in this case, A3 paper), and the print misalignment adjustment values S 1, in bidirectional printing are printed for all print papers having different paper widths. δ 2, δ 3... are sequentially determined. Then, the adjustment values 51, δ2, S3,... Are stored in the print shift adjustment amount memory 202 for each printing paper.

In the method shown in Fig. 5, the print misregistration is not adjusted using multiple print papers.Therefore, when printing on other print paper that has a different paper thickness from the print paper used to adjust the print misalignment, There is a possibility that printing deviation may occur due to the difference. Therefore, for printing paper such as a postcard whose paper thickness is significantly different from the printing paper used for printing the test pattern, the offset of the print shift adjustment amount corresponding to the paper thickness must be offset. Preferably, the adjustment value of the printing deviation is automatically corrected. For example, measure the paper thickness of a postcard in advance, set an offset (adjustment value) of the adjustment amount of the printing deviation caused by the difference in the paper thickness of the postcard, and add the offset to the adjustment value of the printing deviation. You can do so. The offset of the print shift adjustment amount may be stored in the adjustment amount memory 202 separately from the adjustment amounts 51, δ2, <53, ... determined by the method of FIG. Alternatively, the adjustment amounts 51, δ2, S3,... In which the offset is reflected may be stored in the adjustment amount memory 2 2. When switching the offset amount, the paper sensor 308 automatically detects the thickness of the printing paper actually used (the printing paper conveyed by the printer), and switches appropriately according to the detection result. It is possible. At this time, if the offset amount is stored separately from the adjustment values S 1, 6 Ζ, (5 3…, even if the printing paper has the same paper width, an appropriate offset can be set according to the paper thickness. It is possible to correct the adjustment amount of the printing deviation by the amount.

Inspection pattern for all printing papers on one printing paper as shown in Fig. 5 If printing is used, it is possible to adjust the print misregistration using inexpensive printing paper such as plain paper, and use the coat paper postcard to adjust the print misregistration. No need.

In addition, it is also possible to print the inspection pattern at a plurality of positions in the main scanning direction of the printing paper and adjust the print misalignment at these plurality of positions.

For example, as shown in Fig. 6 (a) and 6 (b), the main scanning direction of each printing paper with different paper width is 5 points. The average value of the print misregistration amount at a location may be adopted as an appropriate print misregistration adjustment value. Alternatively, as described later, it is also possible to set a different adjustment amount in each of the five places and adjust the printing position in each of the five places.

In addition, it is possible that the print misregistration amount in both directions differs depending on environmental changes such as temperature. In this case, the print misalignment is adjusted again using one printing paper to determine the re-adjustment value, and the difference from the previous adjustment value is used as the adjustment value for all other papers with different widths or thicknesses. If it is added, it is possible to easily cope with printing deviation due to environmental changes. In any case, it is not necessary to determine the adjustment values for all printing papers again.

In the present embodiment, as shown in FIG. 4, a printer in which the set position of the printing paper is fixed to one of the left sides of the paper feeding tray has been described as an example. In this case, the center position of the printing paper differs depending on the width of the printing paper. For example, in the case of A3 paper, the center position is almost in the center of the scannable section of the print head, and in the case of postcard, the center position is on the left side of the scannable section of the print head (see Fig. 4). Therefore, instead of changing the print shift adjustment value according to the width of the print paper in the main scanning direction, the print shift is determined according to the position of the scanable section of the print head corresponding to the center position of the print paper. It is also possible to change the adjustment value.

As described above, the print shift adjustment values for the forward pass and the return pass are set for each print sheet with a different width in the main scanning direction. This makes it possible to adjust the print misregistration, and to minimize the degradation of print quality due to graininess and rattling, and perform high-speed bidirectional printing. Moreover, once the printing paper has been adjusted, there is no need to adjust it again.

In particular, printing misalignment can be minimized in bidirectional printing of postcards that are very frequently used in home use of ink jet printers.

B. Specific configuration of printer

FIG. 7 is an explanatory diagram showing a schematic configuration of a computer system including a printer as one embodiment of the present invention. This computer system includes a computer 20 and a printer 22. The printer 22 records an image on the printing paper P according to an image signal sent from the computer 20.

The printer 22 includes a sub-scanning drive mechanism for transporting the printing paper P by the paper feed motor 23, a main scanning drive mechanism for reciprocating the carriage 31 in the axial direction of the platen 26 by the carriage motor 24, and a carriage. 31 A printing mechanism that drives the print head 28 mounted on 1 to control ink ejection and dot formation, and a paper feed motor 23, carriage motor 24, print head 28, and operation. And a control circuit 40 for exchanging signals with the panel 32.

The carriage 31 can be loaded with a cartridge 71 for black ink and a cartridge 72 for color ink containing five color inks of cyan, light cyan, magenta, light magenta, and yellow. . A total of six ink discharge heads 61 to 66 are formed in the print head 28 below the carriage 31.

The paper feed motor 23 executes sub-scanning by rotating the platen 26 and other rollers to convey the printing paper P. On the other hand, the carriage motor 24 performs bidirectional main scanning by reciprocating the carriage 31. At the time of the main scanning, the control circuit 40 drives the piezo elements (described later) of the respective printing heads 6 1 to 66 of the printing heads 28 to discharge the respective color inks, and multi-colors the printing paper P. Is formed. The mechanism that transports the printing paper P uses the rotation of the paper feed motor 23 as the platen 26 Instead, a gear train for transmission to the paper transport rollers is provided (not shown). The mechanism for reciprocating the carriage 31 is provided between a carriage shaft 24 and a sliding shaft 34 that is installed in parallel with the axis of the platen 26 and holds the carriage 31 in a slidable manner. It has a pulley 38 on which an endless drive belt 36 is stretched, and a position detection sensor 39 for detecting the origin position of the carriage 31.

The control circuit 40 includes a drive peak generation circuit 44 that generates a drive peak signal CLK that defines the ink ejection timing of the ink ejection head 28. The drive clock generation circuit 44 has a function of changing the ink ejection position (that is, the dot recording position) in the main scanning direction by adjusting the frequency of the drive clock signal CLK. The internal configuration of the drive cook generation circuit 44 will be described later.

Paper sensors 51 to 53 are provided in a paper feed path inside the printer 22. The paper sensors 51 to 53 have paper detection pins 51 a to 53 a at the lower end, respectively. The control circuit 40 detects the width of the printing paper being fed in the main scanning direction according to the combination of the pressed paper detection pins (52 a and 53 a in the example of FIG. 7). It is also possible to detect the thickness of the printing paper according to the amount of the pressed paper detection pins 52a and 53a.

Note that, instead of using the paper sensors 51 to 53, the paper size and paper feed direction (portrait or landscape) set by the user using the printer driver (not shown) of the computer 20 are used. Thus, the width and thickness of the printing paper in the main scanning direction can be determined.

The paper sensors 51 to 53 in FIG. 7 correspond to the paper sensor 308 in FIG. 1, and the print head 28, the carriage motor 24, and the paper feed motor 23 in FIG. 1 corresponds to the print head 3◦2, the carriage motor 304, and the paper feed motor 303. The control circuit 40 in FIG. 40 corresponds to the control unit 200 in FIG.

FIG. 8 is an explanatory diagram showing a schematic configuration of the inside of the ink ejection head 28. ink When the cartridges 7 1 and 2 are mounted on the carriage 31, as shown in FIG. 8, the ink in the ink cartridge is sucked out through the introduction pipe 67 using the capillary phenomenon, and 3 1 The printing head provided at the lower part 28 is guided to each color head 6 1 or 6 6 of 8. When the ink cartridge is installed for the first time, the operation of sucking the ink into the heads 61 to 66 of the respective colors by a dedicated pump is performed. In this embodiment, the pump for suction and the print head at the time of suction are used. Illustration and explanation of the configuration of a cap and the like that cover the door 28 are omitted.

The heads 61 to 66 of each color are provided with a plurality of nozzles Nz for each color, and a piezo element PE, which is one of the electrostrictive elements and has excellent response, is provided for each nozzle. It is located. FIG. 9 shows the structure of the piezo element PE and the nozzle Nz in detail. As shown in the figure, the piezo element PE is installed at a position in contact with an ink passage 68 that guides ink to the nozzle Nz. As is well known, the piezo element PE is an element that performs a very high-speed electric-mechanical-energy conversion by distorting the crystal structure when a voltage is applied. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element P is expanded by the voltage application time as shown in the lower part of FIG. Deform one side wall of passage 6 8. As a result, the volume of the ink passage 68 contracts in accordance with the expansion of the piezo element PE, and becomes ink particles Ip corresponding to the contraction, and is ejected at a high speed from the tip of the nozzle Nz. Printing is performed by the ink particles Ip permeating the paper P mounted on the platen 26.

C. How to correct print misalignment during bidirectional printing:

FIG. 10 is an explanatory diagram showing a method for correcting a print shift during bidirectional printing in the present embodiment. FIG. 10A shows the distribution of the print shift amount ΔX in the main scanning direction when no correction is performed. FIG. 10 (b) shows the corresponding shift in the print position (pixel position) in the forward pass and the return pass. The direction of the horizontal axis X in FIG. 10 (a) is the main scanning direction, which also corresponds to the digit direction of the printing paper. Along the main scanning direction Hereinafter, the width Lmax of the printed printing paper is referred to as “main scanning width” or “main scanning range”. As shown by the solid line in Fig. 10 (b), due to factors such as the warpage of the platen and the extension of the carriage belt, the printing deviation amount ΔX in the forward path and the print deviation amount ΔX in the backward path vary along the main scanning direction. Is changing. The horizontal axis X in FIG. 10 (b) is defined as the coordinate axis of the forward scan in the main scanning direction, and the shift amount ΔX is defined as a value obtained by subtracting the print position of the backward scan from the print position of the forward scan. In the example of Fig. 10 (a), the distribution of the deviation amount △ X along the main scanning direction is convex upward, and takes a positive value at almost the center of the main scanning width Lmax and a negative value at both ends. I take the. However, the zero level of the displacement amount △ X is arbitrary, and in FIG. 10A, the average value of the displacement amount △ X over the main scanning width Lmax is used as the zero level. Note that, depending on the printer, the deviation amount Δ Δ may show a downward convex distribution, contrary to FIG. 1 (a). Since the distribution of the deviation amount ΔX differs for each printer, the deviation amount ΔX on the actual printed matter is measured for each printer.

FIG. 10 (c) shows a distribution of an ideal correction amount 5 for correcting the deviation amount of FIG. 10 (a). Further, FIG. 10 (d) shows the print position of the forward path and the return path when the deviation amount △ X is corrected to be substantially zero. The ideal correction amount <5 is obtained by inverting the sign of the distribution of the deviation amount ΔX shown in FIG. 10 (a).

FIG. 10E shows a change in the frequency f CLK of the drive clock signal C LK (FIG. 7) used to correct the print misalignment in the present embodiment. The main scanning width Lmax is divided into five regions R 1 to R 5 at substantially equal intervals, and the value of the frequency f GLK of the driving clock signal CLK is set individually for each region. L 1 to L 4 indicate the positions of the boundaries of the area. In Fig. 10 (c), the frequency fCLK is set to the standard value f2 in the regions R2 and R4 where the correction amount S is close to zero, and in the region R3 where the correction amount S is negative, the frequency fCLK is higher than the standard value f2. The frequency f CLK is set to a large value f 3, and the frequency f CLK is set to a value f 1 smaller than the standard value f 2 in the regions R 1 and R 5 where the correction amount 5 is positive. The ink ejection timing of the print head 28 depends on the frequency of the drive clock signal CLK. Therefore, the higher the frequency fCLK, the higher the cycle of ink ejection. Becomes shorter, and the distance between the dots in the main scanning direction becomes smaller. The relationship between the change in the dot recording position due to the change in the frequency fCL and the correction of the printing displacement will be described later.

As shown in Fig. 10 (e), if the frequency fCLK of the drive clock signal CLK is individually set for each of a plurality of areas that divide the main scanning range, the ideal correction amount 5 can be approximated. Can be realized. The frequency of the drive clock signal CLK may be changed almost continuously, if the capability of the drive clock generation circuit 44 (FIG. 7) permits. However, as shown in FIG. 10 (e), there is an advantage that changing the frequency f GLK stepwise simplifies the circuit configuration.

By applying the frequency change shown in Fig. 10 (e) on the return path, and maintaining the frequency f GLK at a constant value (for example, the standard value f2) on the outward path, the deviation Δ Δ becomes almost zero. The recording position can be corrected. Alternatively, the frequency f GLK may be adjusted on the outward path, and the frequency f CLK may be maintained at a constant value on the return path. In addition, the frequency may be adjusted on both the outward route and the return route. That is, in general, the frequency f CLK of the drive clock signal CLK may be adjusted in at least one of the forward path and the return path.

It should be noted that the frequency of the main scanning drive signal for driving the carriage motor 24 is maintained at the same constant value in the forward path and the return path. Therefore, if the frequency f GLK of the drive clock signal CLK of the print head 28 is changed as shown in FIG. 10 (e), the recording position (ink discharge position) in the main scanning direction changes accordingly. . However, by changing the frequency of the main scanning drive signal, it is possible to correct the deviation of the recording position in bidirectional printing.

The relationship between the change in the dot recording position due to the change in the frequency f CLK and the correction of the printing deviation is as follows. As described above, the higher the frequency fCLK, the smaller the distance between the dots. In the first and fifth regions R 1 and R 5 in Fig. 10 (e), the frequency f CLK is relatively low, so the distance between dots is relatively large, The recording position is shifted in the minus X direction as compared with FIG. 10 (b). On the other hand, in the third region R3, since the frequency f GLK is relatively high, the distance between the dots is relatively small, and the recording position on the return path is shifted in the plus X direction compared to FIG. 10 (b). Become. As a result, as shown in FIG. 10 (d), the recording position on the return path is corrected so that the recording positions on the outward path and the return path are almost the same. When adjusting the frequency f CLK on the outward path, the frequency f CLK may be changed in the same distribution as in FIG. 8 (e). In addition, the distribution of the deviation amount Δχ can be measured by various methods. For example, when the printer 22 is assembled, the same pattern (for example, a black and white stripe pattern) is printed on the outward path and the return path. Then, the deviation amount Δ 手動 in each of the regions R1 to R5 can be manually measured from the printing result. Alternatively, the printer 22 may be provided with an optical reading device such as a CCD camera or the like, and the shift amount △ X may be automatically measured while printing the same pattern on the outward and return paths. The value of the measured shift amount Δ χ (or the corresponding correction amount S, frequency f1 to f3, or dividing ratio n, m described later) is calculated for each region R1 to R5. Is registered in the control circuit 40 (FIG. 7). D. Internal configuration of drive clock generation circuit 44:

FIG. 11 is a block diagram showing the internal configuration of the drive clock generation circuit 44. The driving clock generation circuit 44 includes a reference clock generation circuit 102, a frequency divider 104, an on / off gate 106, a parameter setting circuit 108, and a programmable ROM (PROM) 110. ing. The reference clock generation circuit 102 generates a reference clock signal RCLK having a predetermined relatively high frequency. This reference clock signal RCLK is frequency-divided by the frequency divider to 1 n to become the drive clock signal CLK. The ON / OFF gate 106 has a function of stopping or restarting the supply of the drive clock signal CLK to the print head 28 in response to a control signal from another circuit in the control circuit 40.

The PROM 110 calculates the division ratios n (R 1) to n (R 5) in each of the regions R 1 to R 5 and the position L 1 to Lmax (or the width of each region) of the boundary between the regions. Remember You. The parameter setting circuit 108 realizes the frequency change shown in FIG. 10 (e) by changing the setting of the frequency division ratio _n in the frequency divider 104. The parameter setting circuit 108 has a counter (not shown) that counts the number of pulses of the drive clock signal CLK output from the on / off gate 1 • 6. By comparing the position "! ~ Lmax" (or comparing the count value with the width of each area), the current main scanning position of the carriage 31 is determined in any of the five areas R1 to R5. It should be noted that the origin position of the carriage 31 is determined in advance by a signal supplied from the position detection sensor 39 (see FIG. 8) to the control circuit 40. The frequency division ratio n corresponding to the area including the main scanning position is read from the PROM 110 and set in the frequency divider 104.

The PROM 110 in FIG. 11 corresponds to the print shift adjustment value memory 202 in FIG. That is, the parameters {n (L1) to n (Lmax), L1 to max} corresponding to a plurality of combinations of the width and thickness of the printing paper are stored in the PROM 110 as adjustment values of the printing deviation. Have been. Further, the entire other circuit elements 102, 104, 106, and 108 in FIG. 11 correspond to the print shift adjusting unit 204 in FIG. As described above, in the drive clock generation circuit 44, only by changing the frequency division ratio n for dividing the reference clock signal RC LK for each region, the drive clock signal C LK having a frequency suitable for each region is obtained. Can be easily obtained. In addition, the method of this embodiment in which the recording position is corrected by adjusting the frequency of the driving signal CLK is simpler in circuit configuration than the conventional method in which the recording position itself is corrected, and is more practical. There is an advantage that it is easy.

By the way, some printers are equipped with a linear encoder for the purpose of correcting a printing displacement caused by the vibration of the carriage. However, it is difficult for a linear encoder to correct the print misalignment caused by the platen warpage. As described in the above embodiment, the driving clock signal CLK of the print head 28 is used. If the frequency is changed along the main scanning direction, it is possible to correct the printing deviation caused by the warpage of the platen. That is, the present invention is effective even when applied to a model provided with a linear encoder for correcting a printing shift. In addition, by applying the present invention to a model in which a linear encoder for correcting a print shift is not provided, both the print shift caused by the vibration of the carriage and the print shift caused by the warpage of the platen can be achieved. Has the effect of being able to simultaneously correct

FIG. 12 is a block diagram showing another configuration of the drive clock generation circuit 44. This drive clock generation circuit 44a is obtained by adding a PLL circuit 120 between the frequency divider 104 and the on / off gate 106 of the circuit 44 in FIG. Also, the function of the parameter setting circuit 108a and the contents stored in the PROM 110 are slightly changed in accordance with the addition of the PLL circuit 120.

The circuit 1_ circuit 120 includes a phase frequency detector (P FD) 122, a low pass filter (LPF) 124, a voltage controlled oscillator (VCO) 126, and a frequency divider 128. I have. This PLL circuit 120 multiplies the frequency of the clock signal CLK divided by the first divider 104 by a multiple of delay m (this is equal to the division ratio of the divider 128). Then, a drive clock signal CLK 'is generated and supplied to the print head 28. The frequency f CLK ′ of the drive clock signal CLK ′ has a value that is mZn times the frequency f RCLK of the reference clock signal R CLK.

The parameter setting circuit 108a sets the drive clock signal CLK 'by setting the frequency division ratios n and m of the two frequency dividers 104 and 128 to values suitable for the respective regions R1 to R5. Can be set to a value suitable for each of the regions R1 to R5. In the circuit shown in Fig. 12, there are two parameters (n and m) for adjusting the frequency, so it is possible to set the frequency in smaller units than in the circuit shown in Fig. 11.

Note that the divider 104 in FIG. 11 and the divider 104 in FIG. The circuit 120 implements a frequency conversion unit (also referred to as a “frequency setting unit”) that generates a drive clock signal by converting the frequency of the reference clock signal RCLK. However, these configurations are merely examples, and other configurations can be adopted as the frequency conversion unit (frequency setting unit).

As described above, in the above embodiment, the recording position is corrected by changing the frequency of the drive clock signal applied to the print head so that the recording position on the forward path and the recording position on the return path substantially match. There is an advantage that print misregistration can be easily corrected with a simple configuration as compared with the case where the position itself is corrected. In particular, since the drive clock frequency is individually set in a plurality of areas where the main scanning width of the printing paper is divided, it is possible to realize a correction close to ideal with a simple configuration.

The adjustment of the printing displacement by changing the frequency of the drive clock signal is performed when the printing displacement is adjusted only at the center position of the printing paper in the main scanning direction, as shown in FIGS. 3 and 4 described above. Is also applicable.

In the above circuit, the main scanning width L max of the printing paper is equally divided into five regions R 1 to R 5, but it is not always necessary to divide the printing paper into equal widths, and it is possible to divide the main scanning width into a plurality of regions with an arbitrary width. It is possible to classify. In addition, the number of area divisions is not limited to 5, and generally, it is sufficient to divide the area into two or more areas. However, since the correction amount closer to the ideal correction amount 5 can be obtained as the number of region divisions increases, it is preferable to divide the scanning width L max into at least five regions.

By the way, even when the main scanning width L max of the printing paper is the same, the main scanning range where the print head 28 actually moves may be limited to a part of the main scanning width L max of the printing paper. For example, when the image is printed only on the left half of the printing paper, the actual main scanning range of the print head 28 is only the left half of the printing paper. In such a case, for example, the value of the printing deviation X at the second position L2 in FIG. 10 (a) is scanned with the printing head 28 over the entire main scanning width Lmax of the printing paper. When printing It may be different from the value of the deviation. The reason for this is that the printing deviation is affected by the elongation of the carriage belt. The carriage belt elongation depends on the acceleration of the carriage. When scanning the entire printing paper main scanning width Lmax, the carriage moves at almost the same speed at position L2, whereas when scanning only the left half of the printing paper, position L2 In, the carriage is accelerating or decelerating. Therefore, even at the same position L2, the value of the printing deviation ΔX differs depending on the actual main scanning range of the print head 28. Considering such a phenomenon, even when the main scanning width L max of the printing paper is the same, the adjustment value (correction amount) of the printing deviation is changed according to the actual scanning range of the printing head 28. It is preferable to set different values for a plurality of positions on the paper.

In the above embodiment, the main scanning is performed by moving the print head. Alternatively, the printing paper may be moved. That is, the present invention is generally applicable to a printer having a bidirectional printing function of performing bidirectional main scanning by moving at least the print medium and the print head relatively.

In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. For example, the functions of a part of the circuits shown in FIGS. 11 and 12 (for example, the parameter setting circuits 108 and 108a) may be executed by a microprocessor executing a computer program stored in a recording medium. It may be realized by. Further, a part (or all) of the functions of the control circuit 40 may be executed by a microprocessor (CPU or the like) of the computer 20.

Recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed materials on which codes such as barcodes are printed, and internal storage devices (RAM, Various computer-readable media, such as memory (ROM) and external storage, can be used. Wear. Industrial applicability

The present invention is applicable to a bidirectional printer that performs bidirectional printing, such as a bidirectional inkjet printer.

Claims

The scope of the claims

1. A printer having a bidirectional printing function for printing an image on a print medium while performing main scanning in both directions in a reciprocating manner,

Print head and

A drive mechanism for moving the printing head and the printing medium at least relatively in the main scanning direction and the sub-scanning direction, and driving the printing head to perform printing on the printing medium;

A control unit that controls the drive mechanism unit,

The control unit includes:

In accordance with the position of the print head in the main scanning direction, the printing position in at least one of the forward path and the return path such that the printing position in the main scanning direction in the forward path substantially coincides with the printing position in the main scanning direction in the return path. Printer with a print misalignment adjustment unit that adjusts

2. The printer according to claim 1, wherein

The printer, wherein the print misalignment adjustment unit adjusts the print position according to an actual main scan range of the print head and a position of the print head in the main scan direction.

3. The printer according to claim 1, wherein

The control unit further includes:

An adjustment value memory for storing an adjustment value used for adjusting the printing position for each of a plurality of printing media having different widths in the main scanning direction;

The print misalignment adjustment unit reads the adjustment value from the adjustment value memory in accordance with the width of the print medium actually used for printing in the main scanning direction, and prints the printing position in accordance with the read adjustment value. Make adjustments for the printer.

4. The printer according to claim 3, further comprising:

A printer comprising a memory for storing data for printing a plurality of print misalignment inspection patterns corresponding to the plurality of print media.

5. The printer according to claim 3, wherein

The printer, wherein the print misalignment adjustment unit corrects the adjustment value of the print misalignment using an offset corresponding to a thickness of a print medium actually used for the printing.

6. The printer according to claim 3, wherein

The printer, wherein the print misalignment adjustment unit adjusts the print position at a central position in the main scanning direction of each of the plurality of recording media.

7. The printer according to claim 3, wherein

A printer that adjusts the printing position at a plurality of positions in the main scanning direction of the plurality of recording media,

8. The printer according to claim 1, wherein

The print shift adjustment unit,

A printer, comprising: a drive clock generation unit that generates a drive clock signal to be applied to the print head and that changes the frequency of the drive clock signal along at least one of the forward path and the return path in the main scanning direction.

9. The printer according to claim 8, wherein

The printer, wherein the drive clock generation unit individually sets the frequency of the drive clock signal in a plurality of areas obtained by dividing a main scanning range. 1 〇. The printer according to claim 9, wherein

The drive clock generator,

An adjustment value memory for storing a parameter for setting a frequency of the drive cook signal for each of the plurality of regions;

A reference clock generating unit that generates a reference clock signal having a predetermined reference frequency; and generating the drive clock signal by converting a frequency of the reference clock signal using a parameter read from the adjustment value memory. Frequency conversion unit to perform

It is determined which of the plurality of areas the main scanning position of the print head is included in, and a parameter corresponding to the area including the main scanning position is read from the memory and sent to the frequency conversion unit. A parameter setting section to be set;

A printer comprising:

11. The printer according to claim 10, wherein

The printer, wherein the parameter setting unit changes a division of the plurality of areas and a value of the parameter according to a width and a thickness of a print medium in a main scanning direction.

12. A method for adjusting a printing position in a main scanning direction in a printer that prints an image on a print medium using a print head while performing bidirectional main scanning in both directions,

In accordance with the position of the print head in the main scanning direction, the printing position in at least one of the forward path and the return path such that the printing position in the main scanning direction in the forward path substantially matches the printing position in the main scanning direction in the return path. Adjust the way.

1 3. The method according to claim 1, wherein

The method of adjusting the printing position according to an actual main scanning range of the printing head and a position of the printing head in the main scanning direction.

14. The method according to claim 12, wherein

Adjustment values used for adjusting the printing position are prepared in advance for a plurality of printing media having different widths in the main scanning direction,

The method of adjusting the print misalignment according to the adjustment value according to the width in the main scanning direction of a print medium actually used for printing.

15. The method of claim 14, further comprising:

The print misalignment inspection pattern for each print medium is printed on each of the plurality of print media, and the adjustment values for the plurality of print media are prepared based on the print misalignment in the print misalignment inspection pattern. How.

16. The method of claim 14, further comprising:

All the plurality of print misalignment inspection patterns for the plurality of print media are printed on one selected print medium among the plurality of print media, and based on the print misalignment in the print misalignment inspection pattern. And wherein the adjustment values for the plurality of print media are provided.

17. The method according to claim 14, wherein

The method according to claim 1, wherein the adjustment value of the printing deviation is corrected using an offset according to a thickness of a printing medium actually used for the printing.

18. The method according to claim 14, wherein

The method according to claim 1, wherein the adjustment of the print misalignment is performed at a central position in the main scanning direction of each of the plurality of recording media.

1 9. The method according to claim 14, wherein

Adjusting the print misalignment at a plurality of positions in the main scanning direction of each of the plurality of recording media.

20. The method according to claim 12, wherein

The method of adjusting the print misalignment by changing a frequency of a drive clock signal applied to the print head in at least one of the forward path and the return path along the main scanning direction.

21. The method of claim 20, wherein

The method according to claim 1, wherein a frequency of the driving clock signal is individually set in a plurality of regions that divide the main scanning range.

2 2. The method according to claim 2, wherein

The setting of the frequency of the drive cook signal,

Parameters for setting the frequency of the drive clock signal are prepared in advance for each of the plurality of regions;

Generating a reference cook signal having a predetermined reference frequency;

Determining which of the plurality of areas the main scanning position of the print head is included in;

Using the parameters corresponding to the area including the main scanning position of the print head, converting the frequency of the reference cook signal to generate the drive cook signal, The way.

2 3. The method according to claim 2, wherein

Depending on the width and thickness in the main scanning direction of the print medium actually used for printing, the A method wherein the division of the number domain and the value of said parameter are changed.